I have been trying to update my husband's Toshiba laptop, but I cannot install Windows XP Service Pack 3 (KB936929). At first the error message I got was the the OS was not validated, so I searched for a fix for that on the Microsoft site, found it and validated the software. So, I don't know what the problem is. I cannot update his Microsoft Office either. I do have Norton 360 installed, is that a problem. Will disabling it fix this? ANd if so, can you walk me through that process? Can anyone help?